What prevents us from developing artificial consciousness?
It may be helpful to think of consciousness, like intelligence, as a spectrum. The Stanford Encyclopedia of Philosophy, under the section &quot;Creature Consciousness&quot; (2.1) defines sentience as:

Sentience. It may be conscious in the generic sense of simply being a sentient creature, one capable of sensing and responding to its world (Armstrong 1981). Being conscious in this sense may admit of degrees, and just what sort of sensory capacities are sufficient may not be sharply defined. Are fish conscious in the relevant respect? And what of shrimp or bees? Stanford Encyclopedia of Philosophy, 2.1 &quot;Creature Consciousness&quot;

It seems clear that AI possesses the most basic form of consciousness in terms of &quot;sensing and responding to its world&quot;.  I might liken this level of consciousness to that of microorganisms, able to interact with their environments but possessing none of the higher functions of humans, or even higher-order animals.
We don't really understand the true nature of higher consciousness and human-level sentience, which doesn't necessarily mean that an automata with sufficient complexity couldn't achieve it.  But there is a deeper problem relating to validation (i.e. how would be know the system is truly self-aware, and not simulating self-awareness.  [See Searle's Chinese Room, but also McCarthy's Refutation] 
In his paper Making Robots Conscious of their Mental
States McCarthy states:

Conscious knowledge and other information is distinguished from
unconscious information by being observable, and its observation results
in conscious knowledge about it. We call this introspective knowledge.
A robot will need to use introspective knowledge in order to operate
in the common sense world and accomplish the tasks humans will give
it.
Many features of human consciousness will be wanted, some will
not, and some abilities not possessed by humans have already been
found feasible and useful in limited domains.
We give preliminary fragments of a logical language a robot can
use to represent information about its own state of mind.
A robot will often have to conclude that it cannot decide a question
on the basis of the information in memory and therefore must seek
information externally.
Programs with much introspective consciousness do not yet exist.
Making Robots Conscious of their Mental
States, Abstract

This still seems to be the case, however, McCarthy seems hopeful about the &quot;computationalist&quot; approach:

Thinking about consciousness with a view to designing it provides
a new approach to some of the problems of consciousness studied by
philosophers. One advantage is that it focusses on the aspects of
consciousness important for intelligent behavior. If the advocates of
qualia are right, it looks like robots won’t need them to exhibit any
behavior exhibited by humans.ibid.

The continual increase in memory, processing and algorithmic sophistication may well yield Artificial General Intelligence.
Even if this proves to be the case, I suspect the debate over artificial consciousness will rage on.

See also: Artificial Consciousness